Optic adaptor junction

ABSTRACT

The disclosure relates to a connector subassembly which provides an optic adaptor junction for a waveguide or an optic transmission line, the connector having a short length of optic waveguide concentrically received within a diametrically resilient ferrule, with one end of the waveguide adapted for concentric alignment with the transmission line, and with the other end located within a cavity of the ferrule which mounts a photoactive section of an optical electronic device in precise coincident alignment with the waveguide.

BACKGROUND OF THE INVENTION

A connector for a light transmitting cable or transmission line isdisclosed in U.S. Pat. No. 3,999,837 and includes a radially deformableresilient ferrule in which is secured the transmission line. Thetransmission line end is polished flush with the end of the ferrule. Theferrule is then inserted into one end of a sleeve form connector whichradially deforms the ferrule, thereby causing the polished transmissionline end to be biased to a stabilized position within the connector.When a second transmission line is provided with a corresponding ferruleand inserted into the other end of the connector, the second waveguideend will also be biased to a stabilized position within the connectorand will be in coincident alignment with the first transmission line sothat light signals may be transferred to one transmission line to theother with low attenuation.

Light signals are generated and received by various photoactiveelectronic circuit elements such as a photodiode, phototransistor or alight emitting diode. Connection of transmission lines to such circutdevices has proven to be time consuming and difficult. Care must betaken to prevent damage to the circuit devices and to minimizeattenuation. It has been difficult also to provide a connection to anoptoelectronic device which may be readily disconnected.

BRIEF DESCRIPTION

A resilient ferrule is adapted for providing a compact coupling of awaveguide and optoelectronic circuit device, which coupling may bereadily disconnected and which provides an optical junction between thewaveguide and circuit device with minimum attenuation. The resilientferrule comprises a portion of a subassembly of the ferrule and a lengthof optical waveguide. The outer diameter of the waveguide isconcentrically enlarged by a build up of suitable material which iscompatible with, or which may be the same as, that material whichalready forms the outer refractive cladding layer of the waveguideitself. The larger diameter assures concentricity of the waveguide corewithin the diameter of the encircling ferrule.

One end of the concentrically enlarged waveguide is polished. A suitablebonding agent is then applied to the enlarged surface of the waveguideor to the interior of the ferrule. The unpolished end of the waveguideis inserted into and along the ferrule interior until the polished endis suitably positioned within a cavity of the ferrule which is toreceive the optoelectronic circuit device.

The ferrule and unpolished end of the waveguide are polished flush witheach other to provide a waveguide and ferrule subassembly which providesan optical coupling element for an optoelectronic circuit device and anoptic transmission line carrying optic signals to or from the circuitdevice.

OBJECTS

An object of the present invention is to provide a compact disconnectcoupling for an optic transmission line and an optoelectronic circuitdevice.

Another object of the present invention is to provide a subassembly ofan optic waveguide polished at both ends and contained concentricallywithin a radially deformable resilient ferrule having a cavity whichmounts a photoactive section of an optoelectronic circuit device inprecise coincident alignment with the waveguides.

Another object of the present invention is to provide a connectorsubassembly which provides an optic adaptor junction for a waveguide andan optic transmission line, the connector having a short length of opticwaveguide concentrically received within the radially deformable,resilient ferrule, with one end of the waveguide adapted for concentricalignment with the transmission line, and with the other end locatedwithin a cavity of the ferrule which precisely mounts a photoactiveportion of an optoelectronic circuit device in precise coincidentalignment with the waveguide.

Another object of the present invention is to provide a couplingconnector having a concentrically enlarged diameter, optic waveguideconcentrically secured in a resilient ferrule which is adapted at oneend for coupling the waveguide to an optic transmission line, and at theother end to an optoelectronic circuit device.

Other objects and many attendant advantages of the present inventionwill become apparent from the following detailed description taken inconjunction with the drawings.

DRAWINGS

FIG. 1 is an enlarged elevation in section of a molded resilient ferruleportion of a connector subassembly according to the present invention.

FIG. 2 is an elevation of the ferrule shown in FIG. 1.

FIG. 3 is an elevation in section similar to FIG. 1 illustrating adiametrically enlarged length of optic waveguide being positioned withina cavity of the ferrule by a gauge block.

FIG. 4 is an elevation in section similar to FIGS. 1 and 3 furtherillustrating an optoelectronic circuit device positioned in coincidentalignment with the length of waveguide and encapsulated in place toprovide an optical junction or adaptor for disengagably coupling atransmission line to the circuit device.

FIG. 5 is an enlarged elevation in section with parts in explodedconfiguration illustrating the details of a connector incorporating theadaptor as shown in FIG. 4 together with a circuit board and atransmission line.

FIG. 6 is a fragmentary elevation in section of the optical connectionof the transmission line and the adaptor.

DETAILED DESCRIPTION

With more particular reference to FIGS. 1 and 2, a resilient ferrule,illustrated generally at 1, is an integral body of plastic materialfabricated by molding, with a reduced diameter cylindrical portion 2provided with a right cylindrical end face 4, a frustoconical section 6,and an enlarged diameter end section 8 having an end face 10. A radiallyprojecting shoulder 11 is provided between the sections 6 and 8. Theinterior of the ferrule 1 is provided with a cylindrical bore 12 whichis concentric with the section 2 and which communicates with the endface 4. The bore extends through at least a portion of the frustoconicalsection 6, communicating with a frustoconical cavity 14, which in turn,communicates with an enlarged, right cylindrical bore 16 having ashallow, right cylindrical counterbore 18 communicating with the endface 10.

The frustoconical cavity 14 is interrupted by a projecting planarprojection 20 defining an enlarged shoulder 22 which joins an arcuateshoulder 24 defined at the junction of the frustoconical cavity 14 andthe enlarged bore 16. A narrow and deeply recessed passageway 26 isprovided in the projection 20 and in the enlarged cylindrical portion 8of the ferrule. The passageway 26 communicates with the frustoconicalcavity 14, the enlarged diameter bore 16, and the counterbore 18, andwith the end face 10 of the ferrule for a purpose to be described. Asshown in FIG. 2, the counterbore 18 provides an arcuate shoulder 28encircling the enlarged bore 16. The shoulder 28 is coplanar with abottom surface of a channel 30 projecting radially from the counterbore18 for a purpose to be described. A flat recessed surface 32 is providedon the circumference of the enlarged diameter section 8 of the ferrulewhich assists in handling and orientation thereof.

The ferrule is fabricated from a plastics material such as any of thepolyesters or polyphenylene sulfide which is relatively rigid yet issufficiently resiliently deformable to allow radial compression of thereduced diameter portion 2 for a purpose to be described.

FIG. 3 illustrates a relatively short length of optical waveguidegenerally illustrated at 34 being assembled with a ferrule 1. One suchwaveguide is available from Galileo Electro Optics Company, Sturbridge,Mass., and is identified as a fiber rod. More particularly, thewaveguide 34 includes an 8 mils. diameter light transmitting core 36 ofglass or plastic material encircled by a cladding material having asuitable refractive index for containing transmitted optic signalswithin the core 36. Initially, the cladding material is relatively thin,on the order of 1 mils, providing an overall diameter of the waveguide34 of about 10 mils. It has been found that the cladding materialinitially is not necessarily concentric with the core 36.

In the desired operation of the resilient ferrule 1, it is importantthat the core 36 be accurately concentric within the reduced diameterportion 2. Accordingly, it has been found necessary to replace orenlarge the cladding layer of the cable 34 by a build up of suitablecladding material to provide an enlarged overall waveguide diameter of40 mils. When enlarging the cladding layer, a build up of the samecladding material of the waveguide is required. The composition of thecladding is available from the manufacturer from which the waveguide iscommercially available. Alternatively, it may be desirable to remove theoriginal cladding material from the core 36. This may be accomplished byuse of a suitable solvent, the composition of which also is madeavailable by the manufacturer of the waveguide. Once the core 36 isentirely free of cladding material, a build up of suitable commerciallyavailable cladding material is concentrically applied thereto.

As shown in FIG. 3, the desired waveguide 34 is one of which the outercladding 38 has been concentrically enlarged to a 40 mil diameter by abuild up of suitable cladding material. The diametrically enlargedwaveguide 34 includes one end 42 which is first polished according towell known techniques to minimize signal attenuation at the end of thecore 36. The opposite end 44 of the waveguide 34 remains unpolished. Thecylindrical exterior of the waveguide 34, or the interior of the bore12, is coated with a relatively thin layer of adhesive such as epoxyresin. The unprepared or unpolished end 44 of the waveguide 34 is theninserted into the enlarged diameter end 8 of the ferrule and along thebore 12 until it protrudes from the face 4. The waveguide 34 will thenbe intimately encircled by the ferrule.

A locating fixture 44 in the form of a generally cylindrical gauge blockof metal or rigid plastic has an outer diameter which interfits withinthe enlarged diameter bore 16 of the ferrule. A flat face 46 of thefixture is seated against the shoulders 22 and 24 of the ferrule. Theface 46 of the fixture is provided with a projecting boss 48 which isprovided with a stepped diameter recess 50 which is received over theend 42 of the diametrically enlarged waveguide 34. With the waveguideseated in the stepped diameter recess 50, and with the fixture 44, inturn, seated against the shoulders 22 and 24 the waveguide is retainedin position until the epoxy resin solidifies and secures or bonds thewaveguide in place within the bore 12. It is noted that the steppeddiameter recess 50 of the fixture engages the polished end 42 of thewaveguide in order to precisely locate the same within the ferruleinterior or cavity. The recess 50 further provides a clearance spacebetween the polished end of the core 36 and the fixture 44 to preventabrasion and consequent damage. Damage to the polished end of the core36 further is avoided by suspending the waveguide end 42 freely withinthe cavity. Any contaminants or residual epoxy resin on the interiorsurfaces of the ferrule are isolated by the free space surrounding thepolished end of the core 36. It has been found that the act of insertingthe waveguide 34 within the ferrule bore 12 will distribute theunsolidified epoxy resin evenly along the length of the bore 12. Epoxyresidue may accumulate at the unpolished end 44 of the waveguide.Further contamination in the form of dust or shavings, produced byabrasion between the waveguide and the interior of the ferrule, mayaccumulate on the end 44 of the waveguide. The polished end 42 of thewaveguide, however, is isolated from such contaminants. When thewaveguide 34 is secured within the ferrule, the unpolished end 44 isthen polished flush with the face 4 of the ferrule, which removes anycontaminants and substantially prevents signal attenuation at the end ofthe core 36. What results is a subassembly of a concentrically enlargedlength of waveguide having polished ends precisely positioned within aferrule having an interior cavity which is suitable for mounting anoptoelectronic circuit device. Such a device has been shown in the formof a can 52 having electrical leads which need to be oriented to effecta correct connection of the leads in a circuit. The tab 64 orients thecan, and thereby its leads, with respect to the ferrule. The flat 32 onthe ferrule then becomes the orienting feature for the ferrule, therebyalso orienting the can and its leads for correct connection of the leadsin a circuit.

It is important that the ratio of the diametrically enlarged waveguide34 as compared with the outer diameter of the cylindrical portion 2 ofthe ferrule is to be selected sufficiently high so that concentricity ofthe core 36 and the outer diameter of the ferrule section 2 isaccurately maintained.

FIG. 4 illustrates one use of the subassembly of FIG. 3 providing aheader package for a standard TO-18 can, shown generally at 52, itself acontainer or package for electronic circuitry which includes aphotoactive circuit element indicated at 54. In the typical case, theelement 54 is mounted on the conductive end 55 of the can 52, and isconnected with a conductive lead 56 to an electrically ground land 58also protruding from an end 55 of the can. The can 52 is of a standarddiameter and interfits within the ferrule bore 16. The end 55 of the canis seated against the shoulders 22 and 24 so that the element 54 isprecisely located in coincident alignment with the end of the waveguidecore 36. Thus, the shoulders 22 and 24 are utilized to preposition theend 42 of the waveguide 34 and also to position the element 54 withinthe interior or cavity of the ferrule 1. The can 52 is, therefore,pluggably received in the ferrule to result in a good optical junctionbetween the element 54 and the waveguide 34. If a permanent mounting ofthe can 52 is desired, a quantity of epoxy resin 60 is deposited withinthe ferrule cavity prior to pluggably inserting the can as described.Upon solidification of the resin, the can will be permanently bonded orsecured at the desired position as shown in FIG. 5. The resin 60 furtherwill bond the end 42 of the waveguide to the element 54. Beforesolidification, some of the resin will be displaced by the can 52.Excess resin will then escape through and along the passageway 26leaving behind sufficient resin to encapsulate and fill the free spacewithin the ferrule interior. The couterbore 18 is allowed to fill withresin in order to encapsulate a radially projecting flange 62 of thecan. As the resin solidifies, some shrinkage may occur; and additionalquantities of resin may be added to fill the counterbore 18. On theflange 62 of some cans a radially projecting tab 64 is sometimesprovided, which is used to polarize or otherwise orient the can. The tab64 will interfit within the recess 30 of the ferrule shown in FIG. 2.Further as shown in FIG. 5, electrical leads 66 and 68 project outwardlyof the can 52 and comprise input and output leads for the electroniccircuitry contained in the can. Typically, the lead 68 is integral withthe conductive end 55 of the can 52. The lead 66 extends entirelythrough the can and protrudes from the end 55 of the can to comprise thelead 58. The conductive end 55 of the can has an enlarged hole (notshown) through which the lead 66 projects without touching theconductive end 55. The can is filled with insulative epoxy resin whichencapsulates and holds the lead 66 in fixed position. The epoxy resin inthe counterbore 18 further encircles the leads 66 and 68 and, thereby,sealably encapsulates the can within the ferrule.

FIG. 5 illustrates a connector assembly utilizing the subassemblies ofFIG. 4 and the can 52 of FIG. 5. More particularly, a typical printedcircuit board 70 having electrical circuit paths 72 and 74 thereonincludes apertures 76 and 78 passing through the circuit paths 72 and74. A can 52 has its electrical leads 66 and 68 passing through theapertures and electrically connected, such as by solder filets 79, tothe corresponding circuit paths 72 and 74. When it is desired to couplean optic cable to the can 52, a cylindrical connector block 80 issecured by fasteners 82 to the circuit board. A radially projecting lip84 of the circuit block 80 overlies the exterior shoulder 11 of theferrule 1, retaining the same against the circuit board 70. The frontend 86 of the connector shell is of concentric sleeve construction. Afrustoconical section 88, between a reduced diameter sleeve form portion90 and an enlarged diameter portion 92, provides radial compression ofthe ferrule 1 when received in the connector shell portion 80.

As shown in FIGS. 5 and 6, the reduced diameter portion 2 of the ferrule1 is compressibly interfitted within a portion of the sleeve portion 90.Radial compression of the sleeve portion 90 on the ferrule portion 2causes resilient radial deformation thereof which biases the waveguide34 to a stable position within the sleeve portion 90. Another resilientferrule 94 is secured to an end portion of an optic transmission line 96having a central core 98 and an outer cladding layer 100. A cylindricalportion 102 of the ferrule 94 is inserted compressibly within the sleeveportion 90. The resilient radial deformation of the ferrule portion 102will bias the core 98 of the transmission line 96 to a stable positionwithin the sleeve 90. In so doing, the cores 98 and 36 will be incoincident alignment, although not necessarily exactly concentric withthe sleeve 90. It has been found that radial compression of two similarresilient ferrules within a common sleeve will bias correspondingoptical cores into coincident alignment, even though the cladding layersare of different diameters, as shown in FIGS. 5 and 6. In addition,radial compression of each ferrule portion 102 and 2 will cause a smallamount of bulging of the ferrule material at their faces 4 and 104.Thus, although previously polished to a planar configuration, thebulging faces 4 and 104 will engage each other and provide a slightseparation between the aligned cores 36 and 98 to prevent abrasion oftheir polished ends against each other. The ferrule 94 is containedwithin an outer sleeve form shell 106, which concentricallly interfitsin the space between the double sleeve form 86 of the connector 80. Anend cap 108 encircles the transmission line and is assembled on the endof the connector portion 106. The cap 108 axially compresses a coilspring 110 which resiliently urges a thrust ring 112 against a shoulder114 of the ferrule 104, causing the ferrule frusto-conical portion 116to seat against a tapered projection 118 of the sleeve 106.

Although preferred embodiments of the present invention are shown anddescribed in detail, other modifications and embodiments are intended tobe covered by the spirit and scope of the appended claims.

What is claimed is:
 1. A coupling connector for connecting between anoptic waveguide transmission line and an optoelectronic circuit device,comprising:a ferrule of resilient material provided with a cylindricalend having a concentric bore therein, an opposite end of said ferruleprovided with a cavity communicating with said bore and being adaptedfor receiving an optoelectronic circuit element, a length of opticwaveguide mounted in said bore and having a polished first endsubstantially flush with said cylindrical end of said ferrule, apolished second end of said waveguide projecting into said cavity at aprecise location within said cavity, first means for seating andpositioning an optoelectronic circuit element at a precise location insaid cavity, and second means for bonding said optoelectronic device andsaid waveguide in said bore .
 2. The structure as recited in claim 1,wherein said second polished end of said waveguide is suspended in freespace within said cavity to avoid contamination thereof.
 3. Thestructure as recited in claim 1, and further including:lighttransmitting encapsulant material along said cavity, said material beingsolidifiable and joining said waveguide and said optoelectronic device,said optoelectronic device including electrical leads protruding fromsaid encapsulant material, a drainage passageway communicating with aportion of said cavity containing said second polished end of saidwaveguide and with an open end of said ferrule for draining excessencapsulant material from said cavity prior to solidification.
 4. Thestructure as recited in claim 1, and further including:a package forcontaining electronic circuitry being provided at one end with aphotoactive circuit element and at the other end of protrudingelectrical leads, said package being seated within said cavity toposition said photoactive element in coincidental alignment with an endof said waveguide, a quantity of solidifiable encapsulant materialwithin said cavity sealably enclosing said package, with said electricalleads protruding outwardly of said encapsulant material and saidferrule.
 5. The structure as recited in claim 1, and furtherincluding:third means for orienting an optoelectronic device in saidferrule, and fourth means for orienting said ferrule.
 6. A method forassembling a coupling connector for connecting between an optictransmission line and an optoelectronic circuit device comprising thesteps of:diametrically enlarging a length of waveguides by a build up ofcladding material concentric with a light transmitting core of saidwaveguide, polishing one end of said diametrically enlarged waveguide,inserting the unpolished end of said diametrically enlarged waveguideinto and along a concentric bore of a radially resiliently deformableferrule, securing said waveguide in said ferrule, polishing the secondend of said waveguide flush with an end of said ferrule, seating anelectronic circuit package within a cavity of said ferrule with aphotoreactive circuit element of said package in coincident alignmentwith a polished end of said diametrically enlarged waveguide,encapsulating said package and said waveguide within a cavity of saidferrule.